Ion producing mechanism



June 10, 1952 J. G. BACKUS 2,600,151

ION PRODUCING MECHANISM Filed Aug. 15, 1946 ATTOR/VEX Patented June 10, l952 UNITED. STATES PATENT ION PRODUCING MECHANISM John G. Backus, Los Angeles, Calii., assignor a the United States of America as represented by the United States Atomic Energy Commission Application August 15, 1946, Serial No. 690,804 (01.

4 Claims.

This invention relates to ion generators and more particularly to ion generators of the type employing electron bombardment of a solid body to be ionized. 1

It is an object of the invention to provide a simple and eflicient ion generator.

Another object of the invention is to provide an ion generator wherein electrons bombard a solid body to produce ions of the material comprising the body.

Other objects and advantages of the invention will be apparent from the following description and claims considered together with the drawing forming an integral part of this specification and comprising an isometric view of apparatus embodying my invention.

Referring now to the drawing it will be seen that an evacuated vessel is formed by means of a glass cylinder l capped on the bottom by a metallic plate 2 and on the top by a metallic plate 3. Appropriate seals are provided to render the vessel air-tight and a pump line 4 is con nected to a pump 6 to evacuate the vessel to any desired degree.

Positioned on the bottom plate 2 is a tripod I made of tungsten upon which is placed a crucible 8 of high temperature insulator, such as alundum. Placed within the crucible is a block of material 9 from which ions are desired; for example, a block of uranium metal has been utilized in this connection. A tungsten wire It is secured to the block 9 and passes through an insulating bushing I2 in the bottom plate 2 to provide an anode lead for the block 9.

Positioned near the top of the vacuum vessel is a coiled filament l3 having two legs l4 passing through the upper cover 3 through insulating bushings [6. A grid ii is mechanically supported by the filament l3 and is maintained at filament potential, and fits completely across the upper interior of the glass cylinder l.

The filament I3 is rendered thermally emissive by a battery is placed across the two filament legs 14, the resistive current heating the filament 13 to a white heat whereupon it emits electrons. The filament I3 is made the cathode of a circuit and the block 9 is made the anode of a circuit by a battery it connected to one of the legs M and to the anode lead II. The upper cover 3 is rendered negative with respect to the filament l3 and the supported grid ill by a battery 2! connected between one leg Hi and the cover 3. An ammeter 22 is placed in the circuit to determine the currents reaching the plate 3.

In operation, the battery it passes current through the filament i 3 rendering'it thermally emissive, the electrons forming a stream 23-whichi strikes the block 9, the anode of the circuit.- The impingement of the electrons uponthe block; 9 creates heat which vaporizes the block 9, caus-v ing the vapor to fill the vacuum vessel. This vapor in turn is bombarded by the electron stream 23, setting up an arc discharge. This are discharge gives rise to an arc plasma which fills the entire vacuum vessel below the grid I? and takes on the potential of the most positive member with which it is in contact, namely, the block 9. The grid I! is therefore negative with respect to the arc plasma and attracts toward it positive ions from the arc plasma. These ions pass through the grid l1 and encounter the negative field of the top plate 3. They are therefore accelerated toward this plate 3, causing a current to flow through the ammeter 22, which current is a measure of the number of ions removed from the arc plasma.

The mechanism just described has been successfully employed in generating ions of uranium. This general structure, therefore, could be used in a calutron or other device wherein ions of uranium or any other metal are desired. Further, it is of general utility as an ion generator or for any other purpose in which ions are desired.

Although I have described my invention with respect to a specific embodiment thereof, it is not limited to this embodiment nor otherwise except by the terms of the following claims.

What is claimed is:

1. A device for producing ions comprising a vacuum envelope, an anode therein made of material to be ionized, an electron emissive cathode that supplies electrons for the bombardment of the material, a grid at cathode potential extending across the vacuum envelope in the region of the cathode, an electrode in the vessel disposed on the opposite side of the grid with respect to the cathode, a current reading meter connected to the electrode, and means for applying potential to the electrode that is negative with respect to the grid.

2. An ion source including a cathode, an anode compirisng a material to be vaporized, means establishing an arc discharge from said cathode to said anode for vaporizing and ionizing a portion of said material, and means for withdrawing form the region of said are at least a portion of said ions.

3. Ion producing mechanism comprising an electron emissive cathode, an anode formed of a material to be ionized and maintained at a positive potential with respect to said cathode whereby an arc discharge is established therebetween and said anode is ionized, a grid electrode disposed on the opposite side of said cathode from said anode and maintained at substantially the same potential as said cathode whereby ions forming the are plasma are attracted thereto, and an electrode from said: cathode 'aridni'aintaihed ata' negative potential with respect to said grid whereby ions t ttiiacted tosaid grid are further attracted there- Largest and toward said electroda- A 4 'on producing mechanism comprising" an material to be ionized aifid di'siiosed'ait a dis-=- jaance from said cathode, saidan'odeand cathode heing disposed internal to said envelope, power supply means maintaining said anode at'afpositive' potential with respect to -said cathode whereby el ctihffi discharg s: establishedlfibetweeii L'saiid cathb'd afid aficdetnereoy vaporizingzthemateri sveessnaaasas, said-electron discharge ioniz'in'g sai "vapofioriaeitafiodqnateriai to produce an arc disthtirghavifig aii arc plasmaincluding posi- S cream-ace;

4 v tively charged ions of said anode material and maintained at substantially the potential of said anode, a grid electrode within said envelope on the opposite side of said cathode from said anod and maintained at the potential of said cathode whereby positively charged ions of said are plasma are attracted thereto, a plate electrode disposed adjaciit said; grid electrode? and? separated from said: cathode by"said gridelectrode, and means maintaining said plate electrode at a negative potential with respect to said grid electrode wherebathe-ions attracted to said grid pass thereth'roiigh and are accelerated toward said plate JOHN G. BACKUS.

REFERENCES CITED The following references are of record in the file of" this patent:

UNITED STATES PATENTS Number Name Datei $221,467 Bleakney vNow-1.11940- 2,323,560 Motz July-G-, 1943 2,507,653 Smith:- .May -16; 1950 

